Anti-Fraud Signup Validation via WhatsApp Profile API
Reject disposable or burner phone numbers at signup by checking whether the number is registered on WhatsApp. Disposable-SMS numbers rarely have WhatsApp accounts — this single signal filters a large share of signup fraud.
The fraud signal
Most disposable-SMS / OTP-receiver services expose numbers whose WhatsApp accounts are either absent or rapidly rotated. Checking isWAContact + profile completeness (about / picture) at signup gives you a low-cost, low-friction first-line filter before you invest in heavier identity verification.
Scoring rules that work
| Signal | Risk weight |
|---|---|
isWAContact: false | High — especially for consumer products where WhatsApp reach is dense |
| Valid, no profile picture, no "about" | Medium — fresh / burner account |
| Business account from a country that doesn't match billing address | Medium |
| Account profile picture set to default / missing thumb | Low (common in certain demographics) |
Tune thresholds per geography. WhatsApp density varies — LatAm / India / SEA ≈ 90%+, North America ≈ 45-60%.
Integration pattern
- User submits signup form with phone number.
- Call GET https://whatsapp-proxy.checkleaked.cc/number/{number} server-side with header x-rapidapi-key: <direct-purchase-key> (never expose the key client-side). RapidAPI marketplace users: swap base URL to whatsapp-data1.p.rapidapi.com and add x-rapidapi-host header.
- Combine the WhatsApp signal with your other fraud signals (IP reputation, email age, device fingerprint).
- For high-risk scores, escalate to SMS OTP or step-up KYC. For low-risk, let the signup complete.
Cost vs fraud-loss math
At $0.005 per check (MEGA tier), a single fraud check costs half a cent. For most SaaS / fintech / e-commerce signups, blocking even a few synthetic accounts per month pays for unlimited checking at this price. Cache results server-side for 24 hours to avoid double-billing on retry-heavy signup flows.
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